Rock duster and method



169-45. DR 2,258 ,117' :sR gggwn m Oct. 7, 1941. E. LAMB ET AL 2,258,117

7 ROCK DUSTER AND METHOD Filed Feb. 17,, 1940 \EEI / INVENTORS [WW/9RD LAMB X} BY slMa/v H. 55H

ATTORNEYS FIRE. LAIIIIUUIDHEHO,

Patented Oct. 7, 1941 ROCK DUSTER AND METHOD Edward Lamb, San Francisco, Calif., and

Simon H. Ash, Trucksville, Pa.

Application February 17, 1940, Serial No. 319,482

8 Claims.

This invention relates to rock-dusters, and has for one of its objects an improved rock-duster adapted to be actuated by fluid under pressure for rock dusting in mines and which device is also suitable for use in distributing powdered material over any desired surface or into any desired area.

Another object of the invention is a rock-duster or the like adapted to be safely used in mines or areas where the use of motors, blowers or the like in sufficiently close proximity to the rock-duster to be relatively effective would be likely to cause an explosion of combustible gas or coal dust.

A still further object of the invention is alight, manually portable device adapted to be actuated by compressed air or gas conducted from a near or remote point, and which device is adapted to be readily and easily manipulated to blow the rock dust, or the like into any desired area or onto any desired surface, and which device is economical in operation and highly eflicient and cheap to make.

Other objects and advantageswill appear in the description and drawing annexed hereto.

In the drawing,

Fig. 1 is a part sectional, partelevational view of the device of this invention as seen from above, part of the rock dust receptacle being broken away to reveal the ejector nozzle therebelow.

Fig. 2 is an end elevation view of the device of this invention, part of the dust receptacle being broken away to accommodate Fig. 3 on the sheet.

Fig. 3 is a side elevational view of this invention, with the outer end of the ejector nozzle broken away to accommodate the view to the sheet.

The practice of rock dusting in coal mines has heretofore been accomplished in several ways, such as by first cleaning the floor, and all projections on the sides, roof, timbers, etc., of coal dust, as much as possible, and thereafter strewing rock dust, such as powdered shale or limestone, that is fairly free from free silica, flint or quartz particles, over the floor and projections, or wherever coal dust may accumulate. This method covers the coal dust with the rock dust and lowers the explosive hazard of the coal dust. In some instances the walls of the mine are washed and then the dry rock dust is applied to form a coating of dry rock dust on the walls while in other instances piles of rock or shale dust have been placed on platforms at various intervals, which dust, including the coal dust, is raised by the air waves caused by an explosion, thereby mixing the rock dust and coal dust to form a less.

combustible mixture that tends to choke the flames, and prevent the propagation of the explosion. More recently the authorities have recommended that, after cleaning the mine, the rock dust should be blown by a motor driven fan over the walls, floor, timbers, etc., so as to raise the dry coal dust and to cause a mixing of the rock dust therewith. This latter practice appears to be most effective, but introduces a new danger, since the production of sufficient air pressure by the blower or fan to be practical requires that the motor and fan be relatively close to the rock dust that isbeing blown thereby, thus a spark from themotor or fan may cause an explosion.

My invention entirely eliminates this hazard, yet produces a more powerful effective air flow than is obtainable by a fan, and the operator is free to work at any point where a compressed air line may be carried. The source of compressed air, may, of course, be at a point remote from the workman, and completely out of the danger zone or area.

In detail, the invention illustrated in the drawing com-prises an elongated tubular discharge nozzle member I, which, for economy of manufacture and lightness, may be of relatively rigid sheet metal witha bead formed around the outer or discharge end, as shown in Fig. 1, for reinforcing said outer end. The inner end of said member is removably secured to a tubular extension 2 from an ejector assembly 3, the latter, including the extension, being preferably a casting, although the entire device may obviously be either cast or fabricated from sheet metal or may be made of any other suitable material.

The inner end of member I may be connected to the extension 2 by a tight friction fit, or by threads or in any other suitable manner, and the bores of said extension and member I are formed in substantial continuation with the walls thereof tapering uniformly from the ejector assembly to the outer end of member I.

The ejector assembly comprises an enlarged cylindrical or annular chamber 4 in axial alignment with the central longitudinal axis of the extension 2 and member I, the walls of said chamber at the end extending convergently at 5 to connect with the extension 2 while a radially inwardly projecting annular flange 6 is formed at the opposite end of chamber 4. Thus the enlarged chamber 4 and extension 2, at their juncture, form, generally, a Venturi throat I, since the convergent walls 5 of the chamber 4 are curved and the walls of the bore in extension 2 extend divergently from the juncture of the latter with the walls 5.

In actual practice the throat I may be of a diameter of say about 1% to about 1 inches and the distance from said throat to the outer end of member I from about 30 to about 36 inches, while the diameter of the outer end of member I may be from about 3 to about 4 inches. These dimensions may be varied, of course, provided the proportions are generally maintained, since for dusting in larger areas the throat diameter may be appreciably larger, and as a consequence the diameter of the nozzle member will increase. However, the taper of the bore from the throat to the outer end of the nozzle member should be relatively slight.

Extending into the chamber 4 from the end thereof opposite throat 'I is a tube 8, said tube being of substantially uniform diameter, but formed with an externally threaded enlarged portion 9 adapted to engage the threaded radially inwardly facing edges of flange 6. The portion of tube extending into said chamber, terminates at its inner end adjacent throat I, and said inner end is preferably positioned slightly inside said throat so that the outer cylindrical sides of said inner end are spaced slightly from the sides of said throat to form an annular aperture communicating between the area within chamber 4 and the area within the bores of extension 2 and nozzle member I. This annular aperture, as a result of the position of the inner end of tube 8 within said throat, will result in air under compression within chamber 8 being directed into the bores of extension 2 and member I along substantially parallel lines, as indicated by the arrows III.

The threaded portion 8 on tube 8 extends outwardly of the chamber 4 a substantial distance, and radially outwardly opening recesses II in said portion 9 positioned outwardly of and spaced from chamber 4 and flange 6, enables an operator to use a spanner wrench or suitable tool, for rotating tube 8 and thereby moving the tube inwardly or outwardly of chamber 4 so as to position the inner end of the tube in the most effective position with reference to the throat I.

A lock nut I2 on the threaded portion 8 serves to lock the tube 8 in the desired position.

The extreme outer end portion of tube 8, positioned outwardly of chamber 4 is removably secured to the restricted, tubular neck I3, of the rock dust intake member. The bore on the neck of said intake member opens at one end directly into the bore of the tube 8, and is of the same diameter so as to create no resistance to the flow of rock dust into said tube. The intake member itself is in the form of an elbow with the neck being one leg thereof, and the other leg that extends substantially at right angles to said neck, instead of being cylindrical, is flattened so the walls of the bore in said other leg extend divergently from the neck to provide: an elongated inlet opening I4, as best seen in Fig. 1.

Over the inlet I4 is secured a hopper I5, which hopper is substantially vertically disposed with a vertically disposed side wall I6 extending upwardly in upward continuation of the edge of the inlet I4 that is farthest from the ejector nozzle, while the side wall I! opposite wall I6 extends slantingly upwardly over the ejector assembly 3. This hopper may be formed integrally with the elbow that connects with tube 8 or may be welded to the elbow, or it may obviously be secured to the latter in any suitable manner. The remaining two opposed walls I8 of the hopper extend convergently from the upper open end of the hopper to the intake I4 and a brace I8, as best indicated in Fig. 3 may coact with the wall H to support the hopper on the ejector assembly 3.

Within hopper I and adjacent wall I8 is a plurality of vertically extending open ended conduits 20 disposed with their upper open ends at the upper open end of the hopper, and with their lower open'ends terminating just above the inlet I4, or just above the juncture of walls I6, I'I, I8

with the elbow that connects with the tube 8, as best seen in Figs. 1, 2.

A compressed air, steam, or gas line 2| opens at one end into the chamber I4, and which line may include a flexible hose 22 communicating with a source of steam, or air, or the like, under pressure. A manually operated valve 28 is positioned adjacent the ejector assembly, and a trap 24 containing some relatively open filter material 25 may be interposed in said line 2| between the ejector assembly and the valve. The portion of the line 2| adjacent said ejector assembly, may be partially supported from the hopper by a brace 26 (Figs. 2, 3).

Extending between the trap 24 and the angle portion of the elbow carrying neck I3, is a relatively small pipe 21 (Fig. 3). The end of pipe 21 that opens into said elbow is directed to eject air into and through neck I3 in a direction axially of the axis of tube 8, but said end of the pipe does not project into the bore in said elbow. Where trap 24 is not used, the pipe 21 connects directly with the compressed air line communicating between the source of power (not shown) and the chamber 4.

A shoulder strap 28 is connected at one end with the upper edge of wall I6 of the hopper while the opposite end of the strap connects with the upper edge of the opposite wall of the hopper.

In operation, the operator connects the flexible hose or line 22 with the pipe 2| and then supports the rock duster assembly heretofore described, from his shoulder by strap 28. In this position, the nozzle member I, when horizontal, is about waist high, and the load of rock dust adapted to be held in the hopper I5 is directly supported alongside the body of the operator. When in this supported position, the nozzle member I is easily grasped by the operator and is swung in any desired direction, such as toward the roof, sides or floor of the mine, and the same can readily be swung in any of the various directions at will and during the actual dusting.

After the rock duster is in the position above described, the valve 23 is opened, and the air in passing through the annular aperture at throat I and out of the discharge end of the member I, draws with it the rock dust in hopper I5 through the tube 8. An extremely powerful blast of air or the like, carrying said rock dust, is thus ejected from member I and into all crevices or ledges where rock dust may accumulate, so that in no possible portion of the mine walls where there is access to air, will there exist any loose coal dust unmixed with the rock dust, thus the danger of any explosion due to coal dust is eliminated.

The provision of the air ducts 20, opening at their lower ends at intake I4 at the lower end of the hopper, together with the injection of air through pipe 21 into the tube 8, positively prevents any clogging of the rock dust in the elbow or intake thereto. Either of these features contributes to this desirable result, and they coact to positively insure against failure of the dust to be carried into the air stream in the extension 2 and member I.

This method of rock dusting in mines as well as the apparatus therefor, is believed to be new, and in this respect a highly important feature to procure the best results is the directional flow given to the air at the throat I, since the directional flow of air in the member I from the throat should be substantially parallel with the central ,y/ 169. HRE EXTINGUISHERS,

Search stem axis of the member i, and not transversely of said axis so as to cause any crossing of the air stream from opposite sides of the aperture at said throat within said nozzle member by reason of convergence of the currents caused by the shape of said aperture.

The trap 24 is not essential Where the airor fluid used is free from dirt or particles that might tend to clog the annular aperture at throat I. In many instances the end of the air line 22 carries dirt from the floor of the mine, such as mud, and if it were not for trap 24, in such instances. the mud or dirt would be carried into chamber 4, and since the aperture at the throat I is relatively small, being about .003 to .005 inch clearance between tube 8 and the throat at any point therearound, there might occur objectionable clogging of the aperture. Naturally the material 25 in the trap is of a character to produce the minimum of resistance to the passage of air therethrough and yet function to trap objectionable dirt particles. This trap is readily cleaned by removing plug 29 in the side thereof.

It might be added that the construction above described may be also used for dusting in orchards, vineyards, fields, etc., where insectides are now sprayed by hand, or in certain instances, by aircraft.

Having described our invention, we claim:

1. A rock duster comprising an elongated tubular nozzle having a bore extending longitudinally therethrough of generally venturi-shape, the restricted throat of said bore being disposed adjacent one end thereof, a tube supported at said one end within and coaxial with said nozzle with its free end cooperating With the Walls of said throat to form an annular aperture within said bore adjacent said throat extending around the Walls of said bore directed toward the opposite end of the nozzle, said opposite end being open, means for supplying a compressible fluid under pressure to said aperture for ejection therefrom into said bore, means for feeding rock-dust to said one end of the nozzle whereby upon ejection of said fluid into said bore said rock dust will be drawn into the fluid for discharge therewith from said open end, and means for conducting atmospheric air to said bore at said one end of said nozzle for supplying atmospheric air to said rock dust adjacent the point where the rock dust is fed into said nozzle.

2. A rock duster comprising an elongated tubular nozzle having a bore extending longitudinally therethrough of generally venturi-shape, the restricted throat of said bore being disposed adjacent one end thereof and the opposite end being open, an inner tube coaxial with said bore extending from said one end to said throat and spaced from the walls of said bore and throat thereby forming a chamber therearound and an annular aperture at said throat communicating between the chamber and the bore of the nozzle extending from the chamber to said opposite end, means for supplying a compressible fluid under pressure to within said chamber for ejection thereof through said aperture toward said opposite end, a container for a supply of rock dust, said tube extending outwardly of said bore at said one end and connecting with said container for conducting rock dust to within said bore and to said aperture, means for supplying atmospheric air to said tube at a point substantially between said container and said tube whereby upon ejection of said fluid into the bore through said aperture, a flow of rock dust and atmospheric air will be induced within said bore toward said opposite end of the bore for ejection therefrom to the area to be dusted.

3. In a construction as defined in claim 2, means for supplying a compressible fluid to said. tube for discharge into the latter in a direction from said container toward the end thereof at said throat for facilitating the movement of the rock dust toward said opposite end.

4. In a construction as defined in claim 2, the means for supplying said compressible fluid to said aperture, including a source of compressible fluid and a conduit therefor connecting between said source and said chamber, and a trap interposed in said conduit arranged and adapted to trap solids that may be in said fluid.

5. In a construction as defined in claim 2, the means for supplying atmospheric air to said tube comprising an air conduit within said receptacle opening at one end to the atmosphere and open at the opposite end thereof Within said container at a point adjacent the connection between the receptacle and tube.

6. The method of rock dusting or the like, that comprises the steps of forcing compressed air from a source of supply through an axially directed annular aperture, thereby inducing a flow of atmospheric air through a central area enclosed by said annular aperture for discharge axially of said annular aperture toward the material to be dusted; feeding rock dust into the induced flow of atmospheric air for being carried therewith to said material; and facilitating the feeding of said rock dust by injecting compressed air from said source of supply into the flow of atmospheric air adjacent the point where the rock dust enters said flow of atmospheric air.

'7. The method of rock dusting or the like, that comprises the steps of forcing compressed air from a source of supply through an axially directed annular aperture, thereby inducing a flow of atmospheric air through a central area enclosed by said annular aperture for discharge axially of said annular aperture toward the material to be dusted; supporting a body of rock dust in communication with said area for movement toward said area; and supplying the atmospheric air for said flow substantially unobstructed by the dust of said body, to said body, at a point within said body, below its upper level, adjacent the said area for mixing with said rock dust at said point and to facilitate the flow of rock dust from said point to said area.

8. The method of rock dusting or the like, that comprises the steps of forcing compressed air from a source of supply through an axially directed annular aperture, thereby inducing a flow of atmospheric air through a central area enclosed by said annular aperture for discharge axially of said annular aperture toward the ma- 

